The conventional soft drink or beer can comprises a substantially cylindrical sheet metal vessel with a disk shaped sheet metal cap sealingly secured to an upper edge of the vessel. Such conventional vessels are formed of recyclable aluminium or steel in a sheet metal process which is well known to those skilled in the art.
The conventional soft drink or beer can contains a single liquid, however it has in the past been proposed to modify such a can by including an internal vessel to hold a second liquid.
An example of such a multi-celled drink container is described in U.S. Pat. No. 4,919,295 to Hitzler. Hitzler uses an obsolete cylindrical outer vessel shape. The currently used cans are formed with a tapered neck in a smooth-necking process from an open topped cylindrical blank. The modern necking process technology results in material savings, enhances resistance to vertical stacking forces, and reduces storage space.
The internal vessel of Hitzler comprises a semi-circular prismatic vessel which abuts one half of the internal wall of the outer cylindrical vessel. The cap of the can of Hitzler is comprised of two semi-circular disk portions which are joined together at their straight sides. The straight sides are joined at their bottom side to the upstanding straight edge of the internal vessel to form a central seam across the top surface of the finished circular cap.
The multi-celled container described by Hitzler suffers from the disadvantage that the two-piece cap member is relatively complicated and difficult to fabricate in practice. The cap is comprised of two portions which must be joined together with the internal vessel at the center line of the cap. In most cases the liquid contained within such vessels is under pressure and the reliability of the seal made between the vessels and the external atmosphere is extremely critical. This is especially true when food products are stored within the cells of the container.
A further disadvantage to the multi-celled container of Hitzler is that the volume of liquid stored in the internal vessel is less than the volume which can be contained in the remaining portion of the outer vessel. Since the cap is sealed along its center line, the volume of liquid within the semi-circular internal vessel is less than one half of the internal volume of the outer vessel due to the wall thickness of the internal vessel.
The inability to contain equal volumes is disadvantageous in that the marketability of the multiple cell container is limited thereby. For example, three multiple celled containers could be used to replace a standard six pack of equal volume. If the liquids in the containers were to be mixed in equal volumes for certain applications such as for example epoxy resin and epoxy setting compounds, the application of unequal volumes would inhibit such use.
A multiple celled container could also be used as a promotional item to sell equal volumes of two of a companies products. For example a beer company may wish to sell a lager and an ale together in a multiple celled container as a promotional sales tool. The inability to sell equal volumes of liquid product in both sides of the multiple celled container adds to production considerations and labelling requirements. As a result, the attractiveness of the multiple celled container as a promotional device is diminished.
Therefore it is desirable to produce a multiple celled container which is easily and simply fabricated with a minimum number of parts but also results in a secure seal between the multiple cells and the outside atmosphere.
It is also desirable to produce a multiple celled container wherein the volumes contained within each separate cell are equal.
To ensure marketplace acceptance of any double vessel container, it is a practical necessity that the latest current shape of outer vessel be used. The outer vessels are formed and printed in massive volumes with existing machinery, and any proposed modification that requires a change to accepted manufacturing procedures would likely be a commercial failure. Therefore it is desirable to produce a multiple celled container wherein the volumes contained within each separate cell are equal and wherein the outer vessel is of the latest commonly used standard shape.